Stator structure for electrical machine

ABSTRACT

A stator structure for a cryogenic electrical machine including a non-conducting inner support shell; a stator winding unit carried by and fixed to the inner support shell and including a central part in which the stator winding conductors extend axially along the inner support shell, two end parts each having a transverse section in which the conductors extend transversely to their axial direction, an intermediate section in which the conductors extend between an end part and the central part, and an end connection section in which the conductors are interconnected in a predetermined pattern; and a non-conducting outer torque shell having transversely extending filaments surrounding and fixed to the stator winding.

Smith, Jr. et al.

MACHINE Assignee:

Filed:

STATOR STRUCTURE FOR ELECTRICAL Inventors: Joseph L. Smith, Jr.,Concord;

Philip Thullen, Dover; James L. Klrtley, Jr., Brighton, all of Mass.

Massachusetts Institute of Technology, Cambridge, Mass.

Aug. 9, 1972 Appl. No.: 279,034

US. (:1 310/sz, 310/61, 310/254 1111.01. H02k 1/32 Field of Search310/10, 40, 43, 45,

References Cited UNITED STATES PATENTS Buchhold 310/52 Madsen 310/52 XStekly 310/11 Punga et al. 310/61 Willyoung 310/54 X 11] 3,781,578 Dec.25, 1973 3,621,315 11/1971 Vasterasetal Primary Examiner-J. D. MillerAssistant Examiner-Mark O. Budd Attorney-Joseph S. landiorio et al.

[57] ABSTRACT A stator structure for a cryogenic electrical machineincluding a non-conducting inner support shell; a stator winding unitcarried by and fixed to the inner support shell and including a centralpart in which the stator winding conductors extend axially along theinner support shell, two end parts each having a transverse section inwhich the conductors extend transversely to their axial direction, anintermediate section in which the conductors extend between an end partand the central part, and an end connection section in which theconductors are interconnected in a predetermined pattern; and anon-conducting outer torque shell having transversely extendingfilaments surrounding and fixed to the stator winding.

7 Claims, 9 Drawing Figures BQTBLSTB PATENTEU SHEET 2 [1F 4 wt N\ DRPATENTEB DECZ 5 I975 saw u or 4 l STATOR STRUCTURE FOR ELECTRICALMACHINE FIELD OF INVENTION This invention relates to a stator structurefor a cryogenie electrical machine, and more particularly to such 'astator structure for use in the absence of the conventional magneticiron support structure present in conventional machines.

BACKGROUND OF INVENTION potential of the machine ground reduces theamount of insulation required for turn to turn differences in potentialas compared to the phase to ground difierences in potential. It alsocreates the potentialfor an increase in the terminal voltage or areduction in the volume of electrical insulation as explained inPolyphase Synchronous Alternators Having A controlled Voltage GradientArmature Winding, Smith et al., Ser. No. 166,083, Filed July 26, 1971.Theeliminatio'n of the iron in the machine also eliminates the slotswhich have conventionally been employed to support the conductorsagainst the magnetic forces present in the machine.

SUMMARY OF INVENTION It is therefore an object of this invention toprovide a new and improved stator structure which eliminates the needfor electrically conducting structural iron to combat the magneticforces acting on the stator winding conductors.

It is a further object of this invention to provide such an improvedstator structure in which the stator winding and. the adjacent supportsform a monolithic structure. I

It is a further object of. this invention to provide such an improvedstatorstructure which is supported either at its ends through themechanical frame of the machine or intermediateits ends by anon-conducting resilient strap and pin support or both.

The invention features a stator structure for a cryogenie electricalmachine including a non-conducting inner support shell, a stator windingunit carried by-and fixed'to the inner supportshell and a non-conductingother torque shell having transversely extending filaments surroundingand fixedto thestator winding. The stator winding unit includes acentralpart in which the stator winding conductors extend axially along theinner support shell, two-end parts each having a transverse section inwhich the conductors extend transversely to their axial direction, anintermediate section ductors are'interconnected" in apredeterminedpattern.

DISCLOSURE OF PREFERRED EMBODIMENT Other objects, features andadvantages will occur from the following description of a preferredembodiment and the accompanying drawings, in which:

FIG. 1 is a diagrammatic, cross-sectional, elevational view of a statorstructure according to this invention;

FIG. 2 is a diagrammatic, elevational view shown with parts incross-section of a superconducting alternator using a stator structureaccording to this invention;

FIG. 3 is an enlarged, fragmentary, diagrammatic, cross-sectional viewtaken along lines 3-3 of FIG. 1 showing the conductors in positionbetween the inner support shell and the outer torque shell;

FIG. 4 is an axonometric view of the stator winding unit with the outertorque shell removed;

FIG. 5 is an enlarged axonometric view of an end part of the statorstructure according to this invention;

FIG. 6 is a fragmentary, enlarged, axonometric end view of the statorstructure according to this invention showing an end section in moredetail;

FIG. 7 is a fragmentary, enlarged, axonometric, end view showing theinsulation and bonding details in an end section according to thisinvention;

FIG. 8 is a side, elevational view of the stator structure according tothis invention with the outer torque shell installed. v

FIG. 9 is a diagrammatic, axonometric view of an alternative support forthe stator structure according to this invention.

There is shown in FIG. 1 a stator structure which in this embodiment isactually an armature structure 10 and will be so referred tohereinafter. Armature structure 10 includes aninner support'shell l2typically made of an insulating material such as fabric reinforcedphenolic or fiberglass reinforced epoxy; inner support shell 12 carrieson it an armature winding unit 14 which is surrounded by an outerinsulating torque shell 16. Armature winding unit 14 includes one ormore conductor layers 18, 20 and includes a central part 22 and two endparts 24 and 26. Each layer includes a plurality of insulated conductorswhich extend axially along inner support shell 12 in the vicinity ofcentral part 22. End part 26 includes a transverse section 28 in whichthe conductors extend transversely to their direction in the centralpart 22, an intermediate section 30 interconnecting central part 22 andtransverse section 28 and an end section 32. Similarly, end part 24includes a transverse section 29, intermediate section 31 and endsection 33. In intermediate section 30 conductor layer 18 may be splitinto two sublayers so that it forms one sublayer 34 which lies alonginner shell 12 and a second sublayer 36 which flares outwardly so thatthere is approximately the distance of one layer between it and innershell 12. Layer 20 may be similarly divided to produce portions 38 and40. Similarly in intermediate section 31 conductor layer 18 may be splitso that it forms one sublayer 35 which lies along inner shell 12 and asecond sublayer 37 which flares outwardly. Layer 20 is similarly dividedto produce portions 39 and 41. The extra space provided by this flaringtechnique is provided to accommodate certain geometric constraints whichare discussed in more detail in the copending application PolyphaseSynchronous Alternators Having A Controlled Voltage Gradient ArmatureWinding, filed July 26, 1971, Ser. No. 166,083, by Jotor in layers 18and 20, in central part 22 and at end parts 24 and 26. Fillets, 42, 44may be provided at each end of central part 22 if the flared portions atintermediate sections 30, 31 are steeper than desirable for formingtorque shell 16. In end part 26 armature structure includes a pluralityof end spacers 46 which are arranged circumferentially about armaturestructure 10 interstitially with the conductors which make up conductorlayers 18 and 20. End spacers 46 are joined to a torque member such astorque flange 48 by means of, bolts 50 which also serve as anchoringmeans for the outer torque she1ll -6. An end flange 52 may also beprovided for supporting the unitary, monolithic armature structure 10.End part 24 contains similar end spacers47, torque flange 49, bolts 51and end flange 53.

Before discussing armature structure 10 in more detail in FIGS. 3 etseq. a brief description of the machine system in which armaturestructure 10 is positioned follows with reference to' FIG. 2. Endflanges52 and 53 are connected to additional flanges 56 and 58,respectively, which are in turn supported on additional flanges 60 and62, respectively, which are mounted to the outer cylindrical frame 64that rests on base '66.

Frames 64 maybe designed to function as an image shield to contain themagnetic field within the machine or an iron shield 68 may be used forthat purpose. Within the stator armature structure 10 is located therotor 70 which carries the field structure; rotor 70 includes cryogenicfield winding 72'and assorted helium Conductor layers 18 and 20 may bemade up of a plurality of conductor bars 112, each of which is formed ofa number of conductor bundles 114. Each of the conductor bundles 114 mayinclude a number of individual strands such as the seven strands 116.Each of conductor bundles 114 is wrapped in an insulating tape 1.18, andeach conductor bar 112 formed of a group of conductor bundles 114 isalso wrapped in an insulating tape 120. Tapes 118 and 120 may be apolyester and glass filament type tape with B stage epoxy resin such assold under the trademark F usaflex by General Electric. Such tapemeltswhen subjected to sufficient heat and then reforms to fuse the bundlesand the bars into one monolithic structure. Since each successiveconductor layer occupies a successively greater circumferential area,some wedging means are required to fill the cross-sectional space whichincreases with increasing radius and to secure the conductor bars inposition. Such wedging means may include the bars themselves if they aremade wedge shaped. In FIG. 3 such wedging means are provided inconductor layer 18 by means of tapered elements 122 which taper toeffectively zero at their lower ends and in conductor layer 20 bytapered elements 124 which taper from a larger to a smallercross-section toward the center of the structure. Tapered elements maybe provided within the conductor bars as well as between them. Theconductor bars 114 may be bonded to adjacent tapered elements to furtherincrease the strength of armature structure 10. Conductor bars 112may'also be bonded to outer torque shell 16, intermediate shell 110andinner support shell 12'to "furtherincr'ease the strength of armaturestructure 10. There may be oneor more intermediate shells such asintermediate shell 110 between each of several layers of conductors orthey may beomitted as shown in FIG. 2 depending upon the overall designof the machine. Between and around conductor bundles 114 are spaces 126which may be used as cooling passages or 82 to provide a measure ofcooling and insulation for the. conductors in layers 18 and 20. Bearings88 and 90 rotatably support rotor at either end; at the end proximatebearing 88 there is acoupli ng 92 for connection to the prime mover, andat the end proximate bearing 'there is a slip ring assembly 94 and ahelium transfer System96 having a helium inlet 98, an outlet 100 forsupplying and recovering helium used to cool the field winding 72 andinterior of rotor 70.

There is shown in FIG. 3 a fragmentary, crosssectional view taken alonglines 3-3 of FIG. 1 with an additional component, intermediate shell110, shown positioned between conductor layer 20 and conductor layer 18Outer torque shell 16 is typically formed of filament wound fiberglassset in an epoxy resin; there should be at least two sets of filamentswhich are alternately wound transversely about the tube to placereinforcing filaments near the principle stress directions to transmitthe torque along the shell. This alternating alternatively conduits maybe installed specifically to provide for the flow of oil or othercooling fluid.

In FIG. 4 there is shown the axially extending conductor bars 112 ofconductor layer 20 in the area of central part 22. Between conductorbars 112 can be seen the interstitially placed tapered elements 124. In

FIG. 4 the flared portions 40, 41 of conductors 112 in conductor layer.20 are more clearly shown and between them can be seen the non-flaredportions 38 and 39, respectively. In eachof transverse sections 28 and29 the conductor-bars take on a helical path and then once again returnto an axial path in erid sections 32 and 33 where they are gripped byend spacers 46 and 47, respectively. Some sublayers follow right handand some left hand helical paths. End spacers 46 and 47 are shownattached to the torque flanges 48 and 49 by bolts 50 and s1.

Theend sections 32 and 33 are physically separated from torque flanges48 and 49 by the spaces 48a and 49a but the torque shell 16 extendsacross those spaces 48a,49a to provide'a mechanicalcon'nection betweenend sections 32 and 33 while maintaining electrical insulation betweenend sections 32, 33 and the grounded torque flanges 48, 49. Theindividual filaments of torque shell 16 loop down into the grooves 48b,4% on torque flanges 48 and 49 and weave about the bolts 50, 51 andother projections to securely lock the torque flanges 48, 49 to thetorque shell 16.

I r The enlarged view of FIG. 5 shows the arrangement of conductors 112and tapered elements 124 in central part 22 and also shows more clearlythe distinction be- I tween the flared portions 40 (and 41) and thenonflared portions 38 (and 39). In between each pair of fingers 46 arethe upwrapped end connections 150 of each conductor bar. Between theseconnections 150 are spacer elements 152 which are made of material suchas phenolic. Between spacer elements 152 the end connections 150 arewrapped in a tape 156, FIG. 6, which may be a tape such as the Fusaflextape referred to earlier as usable in other parts of the armaturestructure 10. A set of end connections 150 may be seen more clearly inthe enlarged view of FIG. 7 where the wrapping technique with the tape156 is shown as a zigzagging technique wherein the tape 156 is unwrappedover one set of end connections 150, under the next set of endconnections 150, over the next set of end connections 150, and so onaround the armature structure. When completed, armature structure 10appears as shown in FIG. 8 completely covered by the outer torque shell16 typically made with a filament glass with an epoxy resin so that atleast a portion of the filaments extend transversely or helically aboutthe armature structure 10 to provide resistance to torque which thearmature structure will be subjected to in use.

This construction produces good local mechanical strength from theconductor bars which run in the axial direction and from the insulatingtape which is wound around the individual strands and around theconductor bars. The bonding material, such as the epoxy resin on thetape in this illustrated embodiment, serves to transmit the stressesfrom insulation to insulation and from conductor to insulation. Thegross circumferential strength results from the outer, inner andintermediate shells which are those illustrated, supra, as being formedof glass fiber and epoxy resin; Increased torsional strength resultsfrom the transverse or helical path taken by the filaments in the outertorque shell and the gross axial strength results from the outer andinner shells as well as thev axially extending conductor bars. The samelayered construction used in the central part 22 or active length of themachine is continued right through the end section of the armaturewindings and strap arrangements 161, 167 may be used, FIG. 9;

pin and strap arrangement 161 includes a first pair of pins 160, 162typically mounted in the base of platform 164. A strap 166 is formed bywinding insulating filaments around pin 160, then one full time aroundarmature structure 10, then around pin 162, then a second full timearound structure 10 and then back around pin 160. This winding cycle iscontinued until strap 166 is built up to required strength. Thefilaments are bonded together with a binder such as epoxy. Second pinand strap arrangement 167 includes a second set of pins 168 and 170,arranged transversely to the first, and a strap 172 which is wound overpin 168 and then follows around armature structure 10 one full time andthen is wound over pin 170, back around structure 10 and back to pin168. By the use of such an arrangement the entire armature structure 10may be supported independent of or in addition to the support providedby the conventional'structure extending from end flanges 52, 53 to thebase 66 as depicted in FIG. 2. The use of a second set of pins arrangedtransversely to the first ensures that the armature structure 10 will beheld fixed in space. In addition a third and fourth set of pins andstraps mounted at the other end of armature structure 10 is used toprovide more rigid support. Ovalizing strains which occur in the centralpart 22 or active.

length of the machine may be accommodated by the structure shown inFIGS. 1 and 2 in as much as armature structure 10 is supported only atthe ends 52 and 53. The support structures 161, 167 shown in FIG. 9 arealso able to accommodate ovalizing strains because of the spring likenature of the strap rigging between the pair of pins. Structures such as161 and 167 are particularly advantageous since they provide adistributed attachment to armature structure 10, and do not interferewith or damage the structure of the outer torque inner support shell andincluding a central part in which the stator winding conductors extendaxially along said inner support shell, .two'end parts each having atransverse section in which said conductors extend transversely to theiraxial direction, an intermediate section in which the conductors extendbetween a said end part and said central part, and an end section inwhich said conductors are interconnected in a predetermined pattern;

an outer torque shell of electrically insulating material extendingbeyond said end sections and having transversely'extending filamentssurrounding and fixed to said stator winding unit for mechanicallysupporting and electrically insulating said stator winding unit from theframe of said machine;

each of said end parts including end spacers for securing saidconductors in the area of a said end section and being interconnectedwith said outer torque shellyand a torque member interconnected with.said torque shell and with said end spacers, and an end memberinterconnected with said torque member and said inner support shell.

2. The stator structure of claim 1 in which said central part includestapered elements lodged between said conductors to compensate fortheincrease in the space between said conductors with increasing radialdistance each of said conductors being bonded to said ta- I 3. Thestator structure of claim 1 in which each of said conductors includes aplurality of conductor bundles, each of which includes a plurality ofconductor strands covered with an insulating bonding material.

4. The stator structure of claim 1 in which said conductors in saidtransverse section extend helically about said structure.

5. The stator structure of claim 1 in'which said conductors in said endsections are separated by spacer elements of electrical insulatingmaterial, and are bonded to said spacer elements, there being a numberof layers of said conductors and said end spacers extending partiallyradially between said conductors in said end sections of the outer mostlayer.

6. The stator structure of claim 2 in which said outer torque shellfilaments are looped about and engage said torque member.

7. A stator structure for a cryogenic electrical maintermediate sectionin which the conductors ex-- tend between a saidend part and saidcentral part, and an end section in which said conductors areinterconnected in a predetermined pattern; an outer torque shell ofelectrically insulating material extending beyond said end sections andhaving transversely extending filaments surrounding and fixed to saidstator winding unit for mechanically supporting and electricallyinsulating said stator winding unit from the frame of said machine; anda first pair of pins positioned on either side of said outer shell andan insulating strap forming a closed path wound about one pin at leastonce, wrapped at least once about said outer shell, wound about theother pin and wound again about said outer shell, and a second pair ofpins positioned on either side of said outer shell and orientedtransversely to said first pair of pins and an insulating strap forminga closed path wound about one pin, wrapped at least once about saidouter shell, wrapped about the other pin, and wrapped again at leastonce about said outer shell, and mounting means for supporting saidpins.

1. A stator structure for a cryogenic electrical machine comprising: aninner support shell of electrically insulating material; a statorwinding unit carried by and fixed to said inner support shell andincluding a central part in which the stator winding conductors extendaxially along said inner support shell, two end parts each having atransverse section in which said conductors extend transversely to theiraxial direction, an intermediate section in which the conductors extendbetween a said end part and said central part, and an end section inwhich said conductors are interconnected in a predetermined pattern; anouter torque shell of electrically insulating material extending beyondsaid end sections and having transversely extending filamentssurrounding and fixed to said stator winding unit for mechanicallysupporting and electrically insulating said stator winding unit from theframe of said machine; each of said end parts including end spacers forsecuring said conductors in the area of a said end section and beinginterconnected with said outer torque shell; and a torque memberinterconnected with said torque shell and with said end spacers, and anend member interconnected with said torque member and said inner supportshell.
 2. The stator structure of claim 1 in which said central partincludes tapered elements lodged between said conductors to compensatefor the increase in the space between said conductors with increasingradial distance each of said conductors being bonded to said taperedelements on either side of it and to adjacent ones of said shells, andbonding material being disposed between and around said conductors tobond them to each other.
 3. The stator structure of claim 1 in whicheach of said conductors includes a plurality of conductor bundles, eachof which includes a plurality of conductor strands covered with aninsulating bonding material.
 4. The stator structure of claim 1 in whichsaid conductors in said transverse section extend helically about saidstructure.
 5. The stator structure of claim 1 in which said conductorsin said end sections are separated by spacer elements of electricalinsulating material, and are bonded to said spacer elements, there beinga number of layers of said conductors and said end spacers extendingpartially radially between said conductors in said end sections of theouter most layer.
 6. The stator structure of claim 2 in which said outertorque shell filaments are looped about and engage said torque member.7. A stator structure for a cryogenic electrical machine comprising: aninner support shell of electrically insulating material; a statorwinding unit carried by and fixed to said inner support shell andincluding a central part in which the stator winding conductors extendaxially along said inner support shell, two end parts each having atransverse section in which said conductors extend transversely to theiraxial direction, an intermediate section in which the conductors extendbetween a said end part and said central part, and an end section inwhich said conductors are interconnected in a predetermined pattern; anouter torque shell of electrically insulating material extending beyondsaid end sections and having transversely extending filamentssurrounding and fixed to said stator winding unit for mechanicallysupporting and electrically insulating said stator winding unit from theframe of said machine; and a first pair of pins positioned on eitherside of said outer shell and an insulating strap forming a closed pathwound about one pin at least once, wrapped at least once about saidouter shell, wound about the other pin and wound again about said outershell, and a second pair of pins positioned on either side of said outershell and oriented transversely to said first pair of pins and aninsulating strap forming a closed path wound about one pin, wrapped atleast once about said outer shell, wrapped about the other pin, andwrapped again at least once about said outer shell, and mounting meansfor supporting said pins.